This invention relates to an apparatus for mounting a vehicle wheel on a testing machine, such as an apparatus for balancing wheels. The invention is particularly directed to improvements in the clamping means employed in such an apparatus. The clamping means must assure the correct alignment and centering of a wheel to be tested or balanced in the apparatus. The wheel must also be positively clamped.
A vehicle wheel may be mounted in a balancing machine on a rotatable spindle, with a counter pressure plate being mounted on the spindle adjacent one side of the vehicle wheel. A clamping plate or the like is mounted on the spindle on the opposite side of the wheel. The clamping plate carries clamping pins, studs, or bolts adapted to engage the mounting holes of a vehicle wheel rim.
A universal clamping device for clamping vehicle wheels of different types to the clamping shaft of a testing apparatus is disclosed in German Utility Model Number 7,434,756. This publication discloses a testing apparatus having a tube shaped supporting member which is clampable to the shaft of a testing apparatus. A flat pressure surface is mounted on the tube shaped member. A clamping device is provided with conical studs or bolts for pressing the rim of a wheel against the pressure surface. The conical studs or bolts are adapted to engage the mounting holes of the wheel rim.
The conical studs or bolts of German Utility Model 7,434,756 are supposed to replace the respective means in German Utility Model 1,885,073. The studs or bolts in this latter publication require, due to their shape, a slotted counter pressure plate so that the pins could extend into the slots in the counter pressure plate in order to positively assure the proper mounting and drive of a wheel.
In accordance with German Utility Model 7,434,756 the clamping studs or bolts should have such a length that their conical portions at the free ends engage the mounting holes of the vehicle wheel rim in a pressing manner while still being spaced from the counter pressure plate. In order to provide clamping pins that are adaptable for the clamping of wheels having different diameters and different attachment holes, it is necessary to design the clamping studs or bolts with a maximum diameter suitable for the clamping of a vehicle wheel having mounting holes of the largest expected diameter. Thus, it is necessary that the clamping studs or bolts have such short contoured or conical ends, that it is not assured that the conical ends would positively find and extend through the mounting holes to engage the counter pressure plate with the wheel rim. Hence, the short contoured or conical ends on the clamping studs or bolts are not satisfactory from the standpoint of insuring positive and correct alignment of the mounting holes because a vehicle wheel may be mounted with the clamping pins engaging a portion of the wheel rim bowl rather than the mounting holes. This is unsatisfactory and such undesirable, faulty mounting of the vehicle wheel may make it impossible to properly balance the wheel since the wheel might take different positions during testing and during balancing.
If the conical portions of the clamping studs were to be extended, in order to assure proper alignment of the vehicle wheels in the testing apparatus, then the danger exists that the clamping pins will extend sufficiently through the mounting holes to engage the counter pressure plate before the wheel is positively clamped. This is particularly true for vehicle wheels having mounting holes of relatively large diameter.